ABS Failure: Causes and Solutions

Hello everyone,
I'm having problems again with my girlfriend's Polo. (Polo 9N 1.4 TDI 75hp, manufactured in December 2003, mileage 50,000 km).
It seems like I really got a Monday car. After having to replace both wheel bearings in January due to loud noises, and having the entire brake system renewed (discs/pads) at the same time, new problems have now arisen:
Am Donnerstag ist meine Freundin mit dem Auto gefahren und musste Feststellen, dass schon bei leichter Betätigung der Bremse das ABS sofort einsetzte. Es war erstmal ein Schock für Sie, weil das Auto so fast nicht anzuhalten war. Um den Fehler auf den Grund zu gehen, habe ich die ABS Sicherung gezogen und bin auch Probe gefahren. ABS war jetzt natürlich aus, aber das Auto hat sich gescheit Bremsen lassen. Wenn man die Sicherung wieder einsetzt, tritt das gleiche Problem wieder auf: Bremse leicht betätigen, ABS setzt sofort ein. Auch bei niedriger Geschwindigkeit. Erst bei vielleicht 10km schien es nicht zu greifen( Stand ja auch fast).Wenn man in diesem Zustand einen Moment gefahren ist, hat es scheinbar auch das Steuergerät gemerkt und gibt ein Akustisches Signal aus. Gleichzeit gehen die Lampe für ABS und ESP an und das ABS ist definitiv aus. (Also gleicher Effekt wie die gezogene Sicherung). Weil ich das Steuergerät auslesen lassen wollte, habe ich meine Freundin damit zum freundlichen um die Ecke geschickt. Im Fehlerspeicher Stand der Fehler „ABS Sensor vorne rechts defekt“ Super habe ich gedacht und gesagt, dann macht mal neu (35€+ Arbeitszeit). Als ich dann abends das Auto abholen wollte, meinten Sie Hmm wir haben da ein Problem. Der Fehler war trotz neuer Sensoren (links und rechts) immer noch da. Na toll, ich habe Ihnen dann die Einverständnis gegeben die Sensorringe an der Antriebswelle zu überprüfen. Dann riefen Sie 2h später an:“ Ja, die Abstände der Ringe sehen auf beiden Seiten anders aus und da sind ja die Bremsen neu, hat da jemand schon mal was gemacht? Außerdem ist da auch Fett überall“ Ich habe Ihnen gesagt, dass im Januar Bremsen und Radlager getauscht worden sind. Die meinten dann, dass es vielleicht falsch zusammengebaut wäre und deswegen das Problem da ist. ( Von Januar bis am Donnerstag waren keine Probleme, schon merkwürdig, oder?) Sie wollten jedenfalls die Antriebswelle ausbauen und mal schauen, ob da alles richtig zusammengebaut wäre. MiI found it ridiculous, and I broke up with my girlfriend.I had someone pick up the car earlier. They looked here and there, but they didn't really make much progress. Especially after the comment "there's grease everywhere," they could have at least checked if maybe a seal was defective, right? Well, I definitely didn't get grease all over the driveshaft after replacing the wheel bearing.
"Of course, I asked about the next steps, and they were as follows: remove the drive shafts on both the left and right sides and check the sensor rings (okay, I'll do that now). If there's no defect there, expose the ABS control unit and check all the wiring to the sensors (approximately 3 hours or more of labor - 1 hour = €76), possibly replace the wiring harness, and possibly replace the ABS control unit. Well, all in all, it's not a cheap option."
Has anyone else experienced a similar problem, or have any ideas?
I'm still hoping that there's a fault in the measurement rings. But if those are okay, we'll have to check the cables. Are there any resistance values that the control unit should have on the sensor cables? Does anyone know such data, or how would you proceed?

Thank you in advance to everyone who takes the time to address my problem and provide answers.

Greetings.
Dirk.

Hi,

First, compare the distances between the sensor rings and the sensors. If the distance is greater on the front right side, and the wheel hubs are the old ones (meaning a new, incorrect hub hasn't been installed), then there are only two possibilities:
- The axle nut is loose, causing the wheel hub to move outwards within the bearing rings. In this case, the wheel bearing is already damaged and needs to be replaced.
- Forgot to install the retaining ring on the wheel bearing, causing the wheel bearing to move outwards.

Please check it quickly, and make sure the wheel doesn't come loose or start spinning on its own.

Best regards, Rainer.

Hello,

Okay, first of all, thank you. On the driver's side, the wheel bearing housing (an original VW part with the same number as the old one) was also replaced because the old one had a defect in the brake caliper mounting. However, the dealership mentioned that on the driver's side, the ring protrudes a few millimeters, which is supposedly correct, while on the passenger side, the ring is too far inside. I definitely didn't forget the retaining rings (I replaced both wheel bearings myself and made sure they were properly seated). I'll check the clearances myself later (I've only had verbal information from the dealership so far) and, if necessary, remove the shaft to inspect the ring (and of course, the bearing and its seating). Perhaps a ring is defective and has moved inward as a result. I hope the wheel bearing hasn't moved outward.

Regards,
Dirk.

Quote:

Perhaps a ring is defective and has therefore moved a piece inwards.

IMHO, the ring is welded to the hub.

Is there a solution to the problem yet?
I have that too!

Address 03: Brake electronics
Label file: DRV\6Q0-907-37x-ESP.lbl
Control unit part number: 6Q0 907 379 M.
Component and/or version: ESP 5.7 front H02 0001.
Encoding: 0003374
Company number: WSC 31224 000 00000
"One error found:"

00285 - Front right speed sensor (G45)
008 - implausible signal.


I've already replaced the speed sensor, but it didn't improve anything.
Three months ago, I replaced both front wheel bearings, and now I'm getting an ESP error.

What other kind of error could it be?

Thank you and best regards.

Good morning.

I completely forgot to report how it went. So, it was definitely due to a low-quality wheel bearing. It shifted outwards, which caused the clearance to the sensor ring to no longer be correct.
On the driver's side, I installed an original VW wheel bearing (which is still okay after approximately 110,000 km). The bearing on the passenger side was an aftermarket part.

Best regards,
Dirk.